This invention relates to exhaust gass recirculators, and more particularly to an exhaust gas recirculator (hereinbelow referred to as EGR) in which a double diaphragm type flow control valve permitting recirculated exhaust gas to be controlled in two stages by a single pressure control valve is disposed in a recirculating passage for coupling the exhaust system and the intake system of an internal combustion engine.
It has hitherto been well known that exhaust gas nitrogen oxides from gasoline engines, which are generally deemed one of the principal factors of air pollution, can be sharply reduced by recirculating exhaust gas. In order to hold the engine function appropriate and to enhance the reducing effect to the maximum, however, the amount of recirculation of the inactive exhaust gas needs to be delicately controlled in dependence on the running state of the vehicle or the engine. It is common practice to control the amount of recirculation of the gas in two stages in response to the running states. Therefore, two diaphragmed control valves are disposed and effect controls individually.